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Intake gaskets
Hi i have a small block 437c.I. I am running afr 195 comp heads and a motown single plane intake. Currently I am using a 1206 gasket but have some issues. First my heads do have crossover port but intake blocks it. Biggest issue is I notice fuel along intake rail where heads and intake meet. I wipe it and then drive it and it comes right back. Not gushing but you can see wetness and clear little bubbles. It is happening on both sides of intake in the center by the two bolts. I have called my head manufacturer as well as the intake manufacture. Afr said to try 1266 since it is thicker the intake guy said I need sealant on the threads. I understand about sealing being nessecary to prevent oil wicking up bolts but that is not my issue. I most Definately have fuel looking like its bubbling out by the #6 and #5 intake runner between gasket on the head. Most everyone I have asked about this is stumped and has no idea what is causing it. Is the 1266 identical to the 1w06 beside thickness. It looks to me lile thickness as well as height could possibly be the issue. Like the gasket is not tall enough to get pinched by the intake. There is good coverave in the center where I see the fuel but by the corner of the intake runner there is barely any gasket sticking out. The runner on my head is 1.26x2.185. Just curius if the 1266 is any taller for better port sealing etc.
Hi Chris,

What an interesting issue. It's rather strange to have fuel leaking out of the intake gasket since there is vacuum present in the intake ports. Are you sure the intake valves on these two cylinders are sealing and not causing some type of back pressure issue?

We checked both AFR and World parts websites to get their port sizes as well as see what gasket they recommend. Both call for a 1205 intake gasket which has port dimensions of 1.28” x 2.09”. World states their port size is 1.18” X 2.00”, AFR states their port size is 1.26” x 2.185” so the 1205 gasket should work but there will be a tiny bit of overlap. If the port size on the intake is smaller, that overlap won't matter. However, things may not always line up as they should and this may cause problems.

Our question to you is: Have the heads or block been decked? If so, this changes the angle between the heads & intake, requiring the intake to be milled so everything lines up correctly. The intake needing to be milled can be verified by looking at the intake gaskets to see if they have been crushed more along the bottom than the top. You can check for uneven compression of the gasket using a micrometer and measuring how much the gasket has been crushed along the bottom compared to the top. If you find more than 0.004”/0.005” difference, then the angle is off and the intake will need to be milled to correct this.

Another question: Is this a street or race engine? If this is a street engine, then we would recommend a 1205 S-3 which has a steel core. Before you assemble it again, lay the gaskets on the heads & intake just to verify that intake port openings are big enough to seal them. If you do need the larger port size, you can use 1206 S-3 as it has the same dimension as 1206 but also has a steel core.

The 1266 gasket has the same port size as the 1206 but if you have an issue where the bottom is being crushed more than the top, the thicker gasket may help with this issue.

Using thread sealer on the intake bolts will prevent coolant or oil wicking but nothing for fuel.

Lastly, we would recommend that you go to (our electronic catalog) find the Performance section and you will be able to look up all the various offerings we have for this engine:

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